Too Much Of A Good Thing? Extreme Performance Athletes May Be At Risk For Cardiac Arrhythmias

You probably know that regular, moderate exercise can result in many health benefits. But you may be surprised to learn that prolonged, intensive endurance exercise on an Olympian scale can actually damage your heart.

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Scientists and doctors have demonstrated that long-term training and competition in extreme endurance sports such as marathons, Iron-Man triathlons, competitive rowing and long-distance bicycle races may cause structural changes to the heart and large arteries.

“Athlete’s heart syndrome” was first described more than 100 years ago as an apparently benign condition in which the elite athlete’s heart enlarges and thickens. For many years, doctors noted that abnormal electrocardiograms were common for extreme athletes, but no evidence pointed to an association with serious arrhythmias or sudden cardiac death. However, there is accumulating evidence that chronic extreme athletic activity may lead to potentially harmful changes in the heart in some individuals.

For example, a review published recently in the Mayo Clinic Proceedings demonstrated that approximately 12% of apparently healthy marathon runners showed microscopic areas of fibrosis, or scarring in the heart chambers. The significance of these changes is not clear, but they could predispose to abnormal rhythms in some cases.

A two-year follow-up revealed that the rate of coronary heart disease was significantly higher in extreme marathon runners than in moderate runners.

A 2011 Swedish study showed that elite cross-country skiers with long years of endurance training had a 29% higher risk of developing a variety of abnormal heart rhythms, some benign as well as some more serious.

Extreme Athletics and Atrial Fibrillation

High-profile professional athletes who are believed to have died of fatal arrhythmias include National Football League star Reggie White, who died at 43 in 2004, and legendary ultra-marathoner Micah True, who died at 58 earlier this year. Boston Celtic Reggie Lewis (age 27 in 1993) and international soccer star Marc-Vivien Foe (age 28 in 2003), are both believed to have succumbed to hypertrophic cardiomyopathy.

Researchers believe high-endurance sports may promote the occurrence of atrial fibrillation in susceptible persons. This arrhythmia, which involves uncomfortable episodes of irregular, rapid heartbeat caused by faulty electrical signals in the heart, is usually not life-threatening. However, in about 5% of those with the condition, it can lead to heart failure and stroke.

“Physicians are becoming increasingly aware that extreme training regimens and endurance-style competitions can, in rare instances, lead to potentially dangerous, abnormal cardiac rhythms,” says Alfred E. Buxton, MD, director of the Clinical Electrophysiology Laboratory at Beth Israel Deaconess Medical Center’s CardioVascular Institute Physicians need to take into account the current research, follow new developments and be prepared to advise certain patients to make lifestyle changes based on the new data, he says.

One Athlete’s Story

Mark E. Josephson, MD, chief of Cardiovascular Medicine at BIDMC’s CardioVascular Institute—and an internationally recognized expert in electrophysiology and catheter ablation—has treated numerous rowers and other high-performance athletes who have suffered from atrial fibrillation. One example is Frederick Schoch, a world-class rowing champion and executive director of Boston’s celebrated annual Head of the Charles Regatta.

Schoch was diagnosed with paroxysmal trial fibrillation in 2009 after he experienced heavy breathing and lightheadness following his crew’s fifth consecutive first-place finish in the Regatta’s “50 and Older” category. Schoch learned that atrial fibrillation can cause blood clots in the left atrium (upper chamber) and can lead to heart failure and stroke. Treatments may include medications (such as beta-blockers or anti-arrhythmic drugs), interventions (such as catheter ablation) and/or surgery.

To regulate his heart rate, Schoch’s primary care physician prescribed the drug diltiazem, but his episodes persisted and he feared he would never be able to compete again.

“Rowing is in my DNA,”says Schoch, whose father was an Olympian rower. “But with afib, I couldn’t even walk up the stairs.”

In 2010, a fellow rower referred Schoch to Dr. Josephson, who has treated more than 1,000 cardiac arrhythmia patients.

Back in the Boat

After hearing Schoch’s story, Dr. Josephson performed a catheter ablation, an interventional procedure that reduces the frequency of paroxysmal atrial fibrillation symptoms about 70% of the time. The procedure typically lasts two hours and involves inserting a catheter through the groin and puncturing the membrane between the heart’s right and left atria. Catheters are placed at the pulmonary veins (which are the source of atrial fibrillation triggers in 90% of paroxysmal afib cases), while the cardiologist delivers a high-frequency, low-voltage current to the site. This burns the tissue to isolate the pulmonary vein from the atrius so that triggers can’t initiate atrial fibrillation.

Schoch spent one night at BIDMC and returned to work two days later. He resumed his training, and in 2011, just one year after his procedure, he led his team to a sixth first-place finish in the Regatta’s senior division. Currently, he is serving as a television analyst commenting on rowing at the Summer Olympic Games. He is also training for the next Head of the Charles Regatta in October.

To be sure, while the findings cited here are unsettling, they shouldn’t discourage anyone from being physically active. For most adults, the American Heart Association recommends 150 minutes of moderate exercise a week (30 minutes a day on five days), or 75 minutes per week of vigorous exercise. Exercise is almost as effective when divided into several shorter periods during the day for convenience.

The result will be increased physical capacity and mental well-being, and a significant reduction in cardiovascular disease risk factors such as high blood pressure, excess weight and unhealthy cholesterol levels. Regular exercise helps fend off not only heart disease and stroke, but also many cancers, osteoporosis, diabetes, arthritis and depression.

“Moderate exercise is certainly good for your heart and your overall health,” says Dr. Buxton. “However, as is usually the case in life, moderation should be the guideline. Beyond 30-60 minutes per day, you may reach a point of diminishing returns. So don’t overdo it, but take comfort in knowing that with the right diagnosis and treatment, atrial fibrillation can be managed successfully.”